Activity-dependent Cellular and Molecular Events Regulating Memory Project Summary Activity-regulated signaling pathways, by transmitting information regarding synaptic inputs to the nucleus and regulating gene transcription, play a vital role in memory. Knowing these processes would benefit the approaches to improve memory. Still, our understanding of the molecular mechanisms that mediate synapse- to-nucleus signaling remains surprisingly incomplete. In particular, details of how synaptically localized transcriptional modulators are transported to the nucleus, activate the transcriptional machinery, their target genes and the neural circuits they serve on are too poorly understood to be harnessed for therapeutic applications. We propose to address this knowledge gap from a new angle that features a behavioral paradigm with various training strength, mutants that activate or inhibit gene transcription, epigenetic analysis, and gene screening. We have developed a training model in the mouse that uniquely positions us to address three aims that together will markedly advance understanding of the fundamental biology of learning-dependent intracellular signaling. Aim 1 will: a) test the molecular mechanism of learning-dependent synapse-to-nucleus transport in the hippocampus following various strength of training, and b) address potential requirements for transcriptional activity using mutants that inhibit or activate transcription. Accomplishment of the proposed work will define the signaling pathways that mediate training responses in gene transcription, establishing the mechanistic framework for analysis of molecular and cellular changes following various strength of training, and contributing an overview of signaling pathway requirements in various memory paradigms that are dependent on the hippocampus. Aim 2 will define the impact of binding between transcriptional activators and changes in histone modifications in response to various strength of training and various transcriptional mutants while addressing the overall hypothesis that epigenetic modifications reflect the transcriptional machinery specific to their corresponding anatomic circuits. We will conduct a detailed analysis of binding between transcriptional cofactors depending on their posttranslational modifications. We will use mutant transcriptional inhibitors and activators to define their role in epigenetic modifications. Aim 3 will characterize specific gene targets of inducible transcriptional coactivators, epigenetic changes on their specific promoters following training with various strength and analyze how these changes affected by mutant transcriptional inhibitors and activators. We will examine in detail the role of these novel gene targets in memory and in particular in enhancement of memory strength. Given unequivocal evidence that memory strength is critical for healthy maintenance, molecular and neural circuitry dissection of learning-dependent mechanisms connecting synapses to the nucleus and gene targets induced by these processes should yield new insights that guide strategies for improving memory strength and human health.